linux-kernel - RE: [PATCH 2/2] usb: musb: Stop bulk endpoint while queue is rotated

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Message-ID: <ff805af7013a45978646bb7aecc2d1e2@THHSTE15D2BE2.hs20.net>
Date:	Fri, 20 May 2016 17:24:25 +0000
From:	Andrew Goodbody <andrew.goodbody@...brionix.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"b-liu@...com" <b-liu@...com>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH 2/2] usb: musb: Stop bulk endpoint while queue is rotated

> From: Sergei Shtylyov [mailto:sergei.shtylyov@...entembedded.com]
> On 05/20/2016 08:06 PM, Andrew Goodbody wrote:
> 
> >>> Ensure that the endpoint is stopped by clearing REQPKT before
> >>> clearing DATAERR_NAKTIMEOUT before rotating the queue on the
> >>> dedicated bulk endpoint.
> >>> This addresses an issue where a race could result in the endpoint
> >>> receiving data before it was reprogrammed resulting in a warning
> >>> about such data from musb_rx_reinit before it was thrown away.
> >>> The data thrown away was a valid packet that had been correctly
> >>> ACKed which meant the host and device got out of sync.
> >>>
> >>> Signed-off-by: Andrew Goodbody
> <andrew.goodbody@...brionix.com>
> >>> Cc: stable@...r.kernel.org
> >>> ---
> >>>  drivers/usb/musb/musb_host.c | 2 ++
> >>>  1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/drivers/usb/musb/musb_host.c
> >>> b/drivers/usb/musb/musb_host.c index 30e0d65..777ff30 100644
> >>> --- a/drivers/usb/musb/musb_host.c
> >>> +++ b/drivers/usb/musb/musb_host.c
> >>> @@ -999,6 +999,8 @@ static void musb_bulk_nak_timeout(struct musb
> >> *musb, struct musb_hw_ep *ep,
> >>>  		/* clear nak timeout bit */
> >>>  		rx_csr = musb_readw(epio, MUSB_RXCSR);
> >>>  		rx_csr |= MUSB_RXCSR_H_WZC_BITS;
> >>> +		rx_csr &= ~MUSB_RXCSR_H_REQPKT;
> >>> +		musb_writew(epio, MUSB_RXCSR, rx_csr);
> >>>  		rx_csr &= ~MUSB_RXCSR_DATAERROR;
> >>>  		musb_writew(epio, MUSB_RXCSR, rx_csr);
> >>
> >>     Can we not clear both in one write?
> >
> > Section 16.3.8.2.2.1.2 of the TRM says to clear REQPKT before
> DATAERR_NAKTIMEOUT.
> 
>     Right, the MUSB programmer's guide also says that. Then a comment
> wouldn't hurt here.

I'll add that for v2, thanks.

Andrew

> > Andrew
> 
> MBR, Sergei